1. Field of the Invention
The present invention is related to a method of forming trenches, and more particularly, to a method of forming trenches by using reverse sidewall image transfer (reverse STI) technology.
2. Description of the Prior Art
In semiconductor manufacturing processes, in order to transfer an integrated circuit layout onto a semiconductor wafer, the integrated circuit layout is first designed and formed as a photo-mask pattern. The photo-mask pattern is then proportionally transferred to a photoresist layer positioned on the semiconductor wafer.
In recent years, with the increasing miniaturization of semiconductor devices, the design rule of line width and space between lines or devices becomes finer, for example down to feature sizes of 65 nanometers (nm), 45 nm and even to 32 nm, making the spacer between semiconductor devices smaller. However, due to the optical proximity effect, the spacer is about to meet the physical restriction in a lithography process. Hence, the researchers are devoted to develop methods to form semiconductor devices with finer size.